This invention relates to methods for the manufacture of decorative articles, and more particularly to a method of manufacture of plastic capped articles having decorative indicia printed directly onto an adhesive layer.
Decorative plaques, emblems, and articles are widely used throughout a number of industries, including the automotive and appliance industry. Many of these decorative articles are formed on metal or plastic substrates onto which a liquid plastic resin is cast. The plastic resin cures to form a convex or positive meniscus-shaped cap over the substrate which gives a lens effect to the printed decorative indicia on the substrate. Such articles are conventionally adhered to their intended surface, such as an automobile or appliance body, utilizing a pressure sensitive adhesive coated on the back of the article substrate.
For example, Waugh, U.S. Pat. No. 4,100,010, discloses a method for the manufacture of plastic-capped decorative articles which utilizes a flat, decorated foil substrate which can be either metal, paper, or plastic. Onto this decorated foil substrate, a liquid plastic resin is cast which flows to the peripheral side walls of the substrate and forms a positive meniscus or lens cap over the substrate. Likewise, Reed, U.S. Pat. No. 4,259,388, also describes a plastic-capped medallion which is formed on a flexible plastic substrate. Both Reed and Gilleo et al, U.S. Pat. No. 4,409,264, describe the use of a non-wetting material or so-called low surface energy dams to confine the flow of liquid plastic resin during casting.
However, the need for thin metal or plastic substrates to provide a surface for printing the decorative indicia and for supporting the cap poses a number of problems in the manufacture of such decorative articles. The cost of such substrates represents a significant portion of the cost of the article. Typically, such substrates have an adhesive backing and are carried on a release liner or other support sheet. The individual articles are formed by a die cutting operation, termed "kiss cutting", where the substrate is cut by the die but the underlying support sheet is not. A considerable portion of the substrate material must then be stripped off of the support sheet ("weeding") and discarded as scrap. This weeding operation introduces a significant labor and time expense to the manufacturing process in addition to producing large amounts of scrap.
Such die cutting operations, as well as embossing of the substrate, may also cause deformation of the substrate or a burring of the edges of the cut out substrates. Such deformation and burred edges introduce problems during the casting of liquid plastic resin onto the substrate and may cause overflow of the resin over the edges of the substrate. Also, kiss cutting sometimes accidently results in partial severing of the underlying support sheet. If that support sheet is held down by vacuum as in Waugh U.S. Pat. No. 4,100,010, then, during resin casting the vacuum may "pull at" the resin through the severed support sheet, causing overflow.
Finally, deformation and curling of the substrate during curing of the plastic resin may also occur because of differences in expansion and contraction rates of the plastic resin and substrate material. For example, as the plastic resin cures, some shrinkage may occur which causes substrate curling.
Accordingly, the need exists in the art for a decorative article and method of manufacture which avoids the problems of the prior art and yet which is relatively inexpensive to manufacture.